Electric motor winding

ABSTRACT

In accordance with the present invention there is provided improved winding retention means for the field coils in the stator of a rotary electric machine, particularly for coils which are wound in place on the field core by an automatic winding machine. As is well known, winding guides are temporarily secured at each axial end of the stator poles. The shuttles of the winding machine wind successive turns of wire around the poles and in the space between the latter and the winding guides. The retention means includes insulated flat steel wire or strips which .[.are secured to the core as by extending.]. .Iadd.extend .Iaddend.through passages or slots formed in the core laminations. These strips extend out from .[.opposite ends of.]. the core .[.and.]. .Iadd.in both directions and are bent to form off-sets which bear against opposite ends of the core to prevent longitudinal displacement of the strips in the apertures. The end portions of the strips beyond the off-sets extend .Iaddend.underneath the winding guides during the winding operation so as to support the coils after the winding guides have been removed and thereafter are bent around the coils so as to securely anchor the latter to the core and retain them in place.

BACKGROUND OF THE INVENTION

Heretofore, field coils have been retained in place .Iadd.in variousways including .Iaddend.strips of metal.[., tape or cord which are bentor tied around the turns at opposite ends of the core and which bearagainst the outer surface of the core, but are not secured to it in anymanner and consequently do not securely anchor the coils to the core..]..Iadd.which are secured to the core by rivets passing through holesformed in the core and strips. These strips must be insulated and thishas been done by either placing a sleeve of insulating material aroundthem before they are riveted in place or by spraying them with an epoxyresin after securing them to the core and at the same time that the restof the core is sprayed. Also, the rivet heads must be insulated as theyare contacted by the field coils and the rivets are in conductivecontact with the stack. If the strips are insulated by sleeves, separatemeans must be employed to insulate the rivet heads. If the core andstrips are insulated by spraying epoxy resin, this would also insulatethe heads, but this type of insulation would be damaged by thesubsequent bending of the strips around the coils. .Iaddend..[.Moreover,such retaining means have not been put in place until after the coilshave been wound and the winding guides removed with the result that someof the turns may cascade, that is fall out of place..].

SUMMARY OF THE INVENTION

During the winding of the field coils by the automatic winding machine,the insulated strips extend out from the opposite ends of the core andthe extending ends .Iadd.beyond the off-sets .Iaddend.are within orunderneath removable wire guides. The guides serve to guide the wire andform it into turns of the coil and to temporarily support the coil..[.and the insulated strips.]. Upon the completion of the windingoperation, when the guides are removed the strips prevent raveling orcascading and then the strips are bent around the coils to securely fixthem to the core.

DESCRIPTION OF THE FIGURES

FIG. 1 is a prospective view of a stator core in accordance with myinvention prior to the winding thereon of the field coils;

FIG. 2 is a prospective view of the core shown in FIG. 1 with the wireguides of an automatic winding machine in place;

FIG. 3 is a view similar to FIG. 2, but showing the field coils wound onthe core;

FIG. 4 is a view similar to FIG. 3, but with the wire guides removed;

FIG. 5 is a view similar to FIG. 4, but showing a finished stator withthe coil retention strips bent around the coils; and

FIG. 6 is a view similar to FIG. 1, but showing a slightly modifiedembodiment of the invention.

Referring to FIG. 1, reference character 10 designates a stator core,usually comprising a stack of laminations stamped from sheet steel andsecured together by rivets 11. Each lamination is formed with polepieces 12 and 14 having inner partial cylindrical surfaces 16. Slots 18extend through the core on opposite sides of pole piece 12, whilesimilar slots 20 are on opposite sides of pole piece 14. A hole 22extends completely through the core at the circumferential center ofeach pole and electrically insulated flat steel strips 24 extendtherethrough. After being inserted, such strip is bent to form off-sets26 which bear against opposite ends of the core to prevent longitudinaldisplacement of the strip in the hole 22.

As shown in FIG. 2, preparatory to automatically winding field coils inthe pairs of slots 18 and 20 respectively, winding forms or wire guides28 are temporarily secured to the core in well known manner, each guidebeing formed with a recess for receiving the projecting end of the strip24. As shown at 30, each guide is spaced from the adjacent end of thecore a distance sufficient to accommodate the coil to be wound.

During the automatic winding operation, which per se forms no part ofthis invention, a pair of wire feeding shuttles pass axially back andforth through the central space between the surfaces 16 and movecircumferentially at the end of each pass so as to lay turns ofinsulated wire in the pairs of slots 18 and 20, and in the spaces 30, toform the field coils 32 and 34 respectively, shown in FIG. 3. When thewinding is completed, the guides 28 are removed and the portions of thecoils extending across the ends of the core are supported by the strips24, as illustrated in FIG. 4, which prevents any of the turns fromcascading or slipping out of place.

The final step is to bend the strips 24 tightly around the coils asindicated at 36 in FIG. 5 to securely anchor the coils to the core 10which prevents even slight movement which could wear insulation off thewires of the coils thus creating shorts and grounds.

The embodiment shown in FIG. 6 is similar to that above described,except that the strips 24 are received in slots 38 formed in the outercircumferential surface of the core 10 and secured therein by a stakingoperation which upsets the metal of the core at points along the slotsas shown at 40.

While I have shown two more or less specific embodiments of myinvention, it is to be understood that this has been done for thepurpose of illustration only, and that the scope of my invention is notto be limited thereby, but is to be determined by the appended claims.

What is claimed is:
 1. In a rotary electric machine, a stator corehaving poles, a field coil comprising a plurality of turns of conductiveinsulated wire wound on each pole and extending axially on either sidethereof, said core being formed with an axially extending aperturetherethrough located at the circumferential center of each pole, and astrip of .Iadd.electrically insulated .Iaddend.bendable metal .[.securedto said core.]. extending through each aperture and axially beyond saidcore in each direction, .Iadd.the extending portion of each strip beingbent to form off-sets which bear against opposite ends of the core toprevent longitudinal displacement of each strip with respect to thecore, .Iaddend.the extending portions of said turns being supported bythe extending portions of said strips .Iadd.beyond said off-sets,.Iaddend.said extending portions of said strips being bent around saidextending portions of said turns for anchoring said turns in fixedposition on said core. .[.2. A device as defined in claim 1 in whichsaid metal strips are insulated..]. .[.3. A device as defined in claim 1in which said strips are off-set at the ends of said apertures and bearagainst the end surfaces of said stator..].
 4. A device as defined inclaim .[.2.]. .Iadd.1 .Iaddend.in which said axially extending aperturesare slots formed in the outer circumferential surface of said stator. 5.A device as defined in claim 4 in which the edges of said slots areupset against said strips to secure the latter in the slots.